In current film fabrication process, whether the obtained film has a uniform thickness or not is the basis for judging the performances of the film. If a single-layered film has a non-uniform thickness, not only the tensile strength and the barrier properties throughout the film, but also the subsequent processing for the film will be influenced. Thus film thickness measurement techniques are widely used in film manufacturing.
Among the existing methods for film thickness measurement, one or more detecting heads with a probe are used to perform lateral contact scanning for the surface of a film sample to be measured in a mechanical probe method (also called a step measurement method). During the scanning, the probe moves up and down with tiny peaks and valleys on the surface of the film sample to be measured, and changes in the height of the probe are converted into electrical signals by a displacement sensor, and finally the signals are recorded to draw a topography of the surface of the film sample to be measured and measure a film thickness of the film sample to be measured.
However, when the film sample is measured by using a step profiler in the step measurement method, the probe will contact the surface of the film sample to be measured. Since the probe has a small diameter, it is apt to damage the surface of the film sample to be measured when in contact therewith. Additionally, when the step profiler measures the film sample to be measured, the probe has to perform lateral contact scanning for the film sample to be measured, which is time-consuming and greatly influences the measurement efficiency.